Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $72.49   5.667%   $76.598   $76.60   $76.60   $76.60  
  Purchase #2 $46.29   10.184%   $51.0042   $51.00   $51.00   $51.00  
  Purchase #3 $202.64   5.445%   $213.6737   $213.67   $213.65   $213.70  
  Purchase #4 $86.53   13.344%   $98.0766   $98.08   $98.10   $98.10  
  Purchase #5 $177.61   5.566%   $187.4958   $187.50   $187.50   $187.50  
  Purchase #6 $240.55   5.141%   $252.9167   $252.92   $252.90   $252.90  
  Purchase #7 $224.67   10.153%   $247.4807   $247.48   $247.50   $247.50  
  7 purchase totals = $1,050.78       $1,127.2457   $1,127.25   $1,127.25   $1,127.30